This invention relates to flourescent lamps. More particularly, this invention relates to flourescent lamps adapted for upwardly recessed mounting within the ceilings of buildings.
Interior ceilings of commercial or residential buildings commonly comprise a sheet material skin consisting of gypsum board (i.e., xe2x80x9csheetrockxe2x80x9d) or acoustic tiles. Where a ceiling comprises gypsum board, panels thereof are typically nailed or screwed to the undersurfaces of ceiling trusses or ceiling joists, causing the panels to span therebetween. Such panels form a thermal barrier or convective heat flow barrier between the living space below the joists or trusses and xe2x80x9cdeadxe2x80x9d spaces between and overlying the joists or trusses.
Where a ceiling comprises acoustic ceiling tiles, such tiles are typically suspended beneath such ceiling joists or trusses by a grid of tile supporting runners and tee bars; such grid being suspended beneath such trusses or joists by wires. As with gypsum board, acoustic tiles form a convective heat flow or thermal barrier between living space below and dead space above. The thermal barrier functions of gypsum boards and acoustic tiles normally enhance the energy efficiency of buildings. Where ceiling lamp fixtures are recessed upwardly within a gypsum board ceiling panel or within an acoustic ceiling tile, the panel or tile is necessarily perforated, compromising the panel""s or tile""s thermal barrier function.
Where a common tungsten filament incandescent lamp is recessed upwardly within such gypsum board or acoustic tile ceiling, heat generated by such lamp commonly necessitates provision of air vents within the light fixture, allowing upward air convection from the living space below, across the bulb, through the vent, and thence into the dead space above. Such upward air convection beneficially cools the incandescent lamp and the recessed fixture. However, such vents undesirably degrade or limit the thermal barrier function of gypsum board or acoustic ceiling tile within which such fixture may be installed.
A flourescent light tube which emits visible light equivalent to that of a 100 watt incandescent bulb will typically emit less infrared light or radiant heat than that of a 25 watt incandescent bulb. Thus, where flourescent light tubes are recessed upwardly within such gypsum board or acoustic tile ceilings, there typically is little need for providing air convection apertures. However, unlike common incandescent lamps, flourescent lamps typically comprise a phosphor lined argon and mercury vapor filled tube and an iron or electronic ballast, both of which are subject to periodic failure. Thus, where a flourescent light tube is upwardly recessed within such gypsum board or acoustic tile ceiling, the fixture desirably facilitates convenient removal and replacement of both the ballast and the light tube, in addition to preserving the thermal barrier characteristics of the gypsum board or acoustic tile.
Common recessed flourescent light fixtures undesirably compromise the thermal barrier function of the fixture in favor of enhancing interchangeability of the ballast and/or the flourescent tube. The instant inventive recessed flourescent light fixture ameliorates said common undesirable trait of recessed flourescent light fixtures by providing structures which adapt the fixture to simultaneously facilitate interchangeability of the ballast, facilitate interchangeability of the flourescent light tube, and preserve a ceiling""s thermal barrier function.
The instant inventive lamp is preferably recessable upwardly into a gypsum board or acoustic tile ceiling. Suitably, the lamp may be recessed within other types of sheet ceiling materials. A primary structural component of the inventive lamp comprises a cylindrical ceiling aperture lining flange, said flange defining an air dam receiving space. Preferably, the height of such flange is equivalent to the thickness of the gypsum board or acoustic tile within which the inventive light fixture is to be upwardly recessed. The horizontal cross-sectional shape of such flange preferably compliments the shape of the flourescent light tube which the fixture is intended to support and illuminate. For example, where the intended flourescent light tube is circline (a preferred configuration), such horizontal cross sectional shape is preferably circular. For further example, where the flourescent light tube is linear and horizontally mounted, such cross-sectional shape is preferably rectangular. In practice, the flange is preferably, fixedly, and rigidly attached to the ceiling so that it nests within and closely lines an aperture cut through the gypsum board or acoustic tile.
While the cylindrical ceiling aperture lining flange may suitably be attached directly to the apertured gypsum board or acoustic tile, such flange is preferably mounted upon ceiling trusses or ceiling joists which overlie and suspend the gypsum board or acoustic tile. Alternately, the flange may be mounted upon runners of a drop ceiling grid. Necessarily, the ceiling attachment of such flange rigidly positions such flange within the aperture within the gypsum board or acoustic tile.
Numerous ceiling mounting means may be suitably utilized for attaching the cylindrical ceiling aperture lining flange to the ceiling""s trusses or joists. For example, bars or braces spanning between an upper edge of said flange and said joists, trusses, or runners may be provided. As a further example, steel or aluminum wires may be utilized to interconnect said flange and trusses, joists or runners. However, preferably, the means for attaching said flange to such joists, trusses, or runners comprises a support frame including a rectangular steel mounting plate having an aperture there through, the aperture closely matching the dimensions of the cylindrical ceiling aperture lining flange. Suitably, the upper end of such flange may be spot-welded to such plate so that such flange extends downwardly from the edges of such aperture. Alternately, the flange may be formed from the edges of the mounting plate""s aperture through metal bending.
Suitably, the dimensions of such rectangular plate may be approximately 14xc2xd inches by 21xc2xd inches, such dimensions allowing such plate to span between typical 24 inch xe2x80x9con centerxe2x80x9d mounted ceiling trusses, or between 16 inch xe2x80x9con centerxe2x80x9d mounted ceiling/floor joists. Where ceiling trusses or joists are mounted in such standard fashion and where the peripheral edges of such rectangular plate are upwardly flanged, such plate may be conveniently installed between such trusses or joists by nailing through such flanges directly into the side walls of such trusses or joists. However, such plate preferably has smaller dimensions, allowing for convenient installation between variously positioned ceiling trusses, joists, or other structures such as drop ceiling runners. To facilitate universal installability, the preferred ceiling mounting means comprises such smaller rectangular steel plate having its peripheral edges formed to include brace clips; such clips being adapted for engaging telescoping xe2x80x9cTxe2x80x9d braces, whose distal ends are preferably adapted for nailing directly onto the side walls of ceiling trusses or joists, or adapted for mounting upon other structures such as drop ceiling runners.
Necessarily, the instant inventive light fixture comprises a flourescent light tube actuating ballast. Preferably, such ballast is an electronic ballast. Suitably, such ballast may be an iron ballast. Means for removably mounting the ballast upon the upper end of the cylindrical ceiling aperture lining flange are necessarily provided. Suitably, said means may comprise a bracket extending upwardly and outwardly from the upper end of said flange, the ballast being attached to a distal end of said bracket by means such as spirally threaded screws, spirally threaded bolts, slip joint attachments, or other common removable fasteners. Preferably, the removable ballast mounting means comprises the preferred rectangular mounting plate, the ballast being attached to the plate by spirally threaded screws, or other common removable fasteners. Preferably, the ballast is positioned upon the plate so that alternate installation and removal can be effectuated manually from below through the air dam receiving space of the cylindrical ceiling aperture lining flange.
The inventive light fixture""s function as a thermal barrier is primarily accomplished by provision of a concave air dam having an inner surface defining a flourescent light tube receiving space. Preferably, the concave air dam is fitted for upward extension through the air dam receiving space of the cylindrical ceiling aperture lining flange, and preferably the lower lip of said air dam forms and out-turned trim retaining/slide stopping flange. Preferably, the inner surface of the air dam is reflective, enhancing the lamp""s illuminating capability. Also preferably, a side wall of the concave air dam has a wire receiving aperture through which the ballast""s output wires extend. Where such wire receiving aperture is provided, a rubber annular air seal spanning the annulus between said wires and the edges of said aperture is also preferably provided.
Means for removably and interchangeably mounting the concave air dam within the air dam receiving space of the cylindrical ceiling aperture lining flange are necessarily provided. Suitably, said means may comprise a bracket or brace spanning between an exterior side wall of the air dam, and a ceiling mounting means structure such as the preferred rectangular plate. However, the air dam mounting means preferably directly interconnects the concave air dam and the cylindrical ceiling aperture lining flange. Suitably, spirally threaded screws may be utilized to accomplish such interconnection. Preferably, such interconnection is accomplished by a friction mount such as friction clips which allow alternate manual installation of the air dam into and extraction of the air dam from the cylindrical lining flange through application of alternate pulling and pushing forces.
Finally, means for removably mounting the flourescent light tube upon the inner surface of the concave air dam are provided. Suitably, said means may comprise a simple shelf bracket upon which the tube rests. Ties or straps spanning between the tube and the inner wall of the air dam may also be suitably used. However, preferably, said removable mounting means comprises a plurality of arcuately formed spring clips adapted for engaging and holding the curved walls of the flourescent light tube. Proximal ends of such clips are preferably riveted to the inner wall of the air dam.
In some installation environments the ballast and air dam of the instant inventive flourescent light fixture is undesirably exposed within the dead space which overlies the gypsum board or acoustic ceiling tile. Where such dead space serves as an attic, an exposed ballast or air dam may become damaged by persons walking within the attic. Also, blown or rolled insulation within the dead space may undesirably interfere with the functions of the ballast and air dam. Where such concerns exist, a shroud is preferably provided to protect the ballast and the air dam from damage or encroachment of insulating material. While the shroud may suitably be configured as an open frame or grid, the shroud preferably comprises a box, which in combination with the preferred steel plate mounting means, forms an substantially occlusive closure. Where such a shroud is provided, the ballast mounting means preferably comprises one of the shroud""s side walls, the ballast preferably being attached to one of said wall""s inner surfaces by means of spirally threaded screws. Also, where such shroud is provided, the ballast""s input power wires preferably extend through an aperture within said side wall, and thence into an electric junction box fixedly attached to the exterior surface of said side wall, the junction box providing for secure attachment of a protective electric conduit.
Accordingly, it is an object of the present invention to provide a recessed flourescent light fixture which facilitates convenient ballast removal and replacement, convenient flourescent light tube removal and replacement, and which preserves thermal barrier characteristics of gypsum board, acoustic tile, or other sheet ceiling material within which such light fixture is recessed.